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ECE :: Materials and Components

  1. In crystalline solids, atoms are stacked in a regular manner.

  2. A.
    True
    B.
    False

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  3. The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called

  4. A.
    Weiss temperature
    B.
    Curie temperature
    C.
    Neel temperature
    D.
    None of the above

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  5. In metals, the average drift velocity of electron per unit field is called mobility.

  6. A.
    True
    B.
    False

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  7. Ferrites have

  8. A.
    a low copper loss
    B.
    low eddy current loss
    C.
    low resistivity
    D.
    higher specific gravity compared to iron

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  9. In intrinsic semiconductors, the number of free electrons is equal to the number of mobile holes.

  10. A.
    True
    B.
    False

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  11. When a material becomes a superconductor, its resistivity becomes

  12. A.
    very small
    B.
    zero
    C.
    about 10% of normal value
    D.
    about 20% of normal value

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  13. In a piezoelectric crystal, the application of mechanical force will cause

  14. A.
    plastic deformation of crystal
    B.
    magnetic dipoles in the crystal
    C.
    electrical polarization in the crystal
    D.
    shift in Fermi level

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  15. Consider the following statement
    If an electric field is applied to an n type semiconductor bar, the electrons and holes move in opposite directions due to their opposite charges. The net currents is

    1. both due to electrons and holes with electrons as majority carriers
    2. sum of hole and electron currents
    3. difference between electron and hole currents.
    Which of above statements are correct?

  16. A.
    1 only
    B.
    1 and 2
    C.
    2 only
    D.
    3 only

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  17. As the temperature of a pure silicon specimen is increased

  18. A.
    the number of free electrons increases
    B.
    the number of holes decreases
    C.
    the number of holes increases
    D.
    the number of free electrons and holes increases

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  19. Assertion (A): In many materials, dielectric polarization causes mechanical distortion.

    Reason (R): If dielectric polarization causes mechanical distortion then mechanical distortion must cause dielectric polarization.

  20. A.
    Both A and R are true and R is correct explanation of A
    B.
    Both A and R are true but R is not correct explanation of A
    C.
    A is true but R is false
    D.
    A is false but R is true

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